Method and apparatus for manufacture of metallic pellets



March 20, 1956 s. KASSEL METHOD AND APPARATUS FOR MANUFACTURE OFMETALLIC PELLETS Filed April 19, 1952 F IE 1 MOLTEN. METAL RISING VAPORSQUENCHING AND RECEIVING CHAMBER DROPPING BOX STEAM COLLECTING ZONE WATERINLET DESCENDING ANNULAR COLUMN OF WATER! PELLET OUTLET INVENTOR: LOUISS. KASSEL ATTORNEYS:

United States Patent METHOD AND APPARATUS FOR MANUFACTURE OF METALLICPELLETS Application April 19, 1952, Serial No. 283,175

5 Claims. (Cl. 182.7)

This invention relates to an improved method and means for formingsubstantially spherical pellets from a desired molten metal or alloy.

Pellets in substantially spherical or shot form are useful for variouspurposes. For example, shotted lead is used in large quantities for firearms, while aluminum shots or pellets may be used in deoxidizing steel,catalyst manufacture, and many other processes. Round shot andsubstantially spherical pellets may be formed, as they have been formany years, by dropping small metal globules through a considerableheight in a shotting tower, where a molten metal stream is passed from adropping box through a plurality of orifices, or through a screen, sothat a multiplicity of molten globules fall through a high tower andinto a suitable quench chamher; having water or other liquid medium orgaseous medium.

It is, however, undesirable in many instances to provide a high coolingtower permitting a long free fall of molten particles. Also, thedropping of molten globules directly into a liquid containing chamber isgenerally undesirable, particularly from the aspect of obtainingspherically shaped particles, since many metallic materials tend toflatten out when they hit the surface of water or other liquid.Particles which are not sufficiently cooled and which fall into a liquidreceiving chamber may agglomerate as they pass downwardly therethroughand thus provide still another difficult'y in the collection ofresulting pelleted particles.

It is, therefore, a principalobject of the present invention to providean improved method and means for cooling and forming substantiallyspherical pellets from a molt'en'metal in a manner which precludes theneed of an excessively long fall of the molten globules.

It is also an object of the present invention to provide for the fall ofmolten metal globules downwardly through an encompassing and closelyconfining ring-like stream so that particles may be cooled and take aninitial set before passing into a receiving chamber.

Other objects and advantages of the present method of forming pelletswill be apparent from succeeding portions of the description and uponreference to the accompanying drawing.

,Briefly, the method of manufacturing metallic pellets in accordancewith the present invention, embodies passing moltenmetal downwardthrough an orifice and forming discreet globules of the metal, droppingsuccessive metallic globules from'the orifice downwardly through aclosely confining tubular film of cooling fiuid, efiecting the coolingof the globules and discharging resulting cooling metal pellets from theconfines of the lower end of the tubular fluid film.

In carrying out the present invention, water or other suitable liquidmedium may be allowed to overflow circumferentially into the top end ofa vertically disposed tubular member so that a liquid film covers theentire inner surface of the tubular member in a continuous downflowingtubular or ring-like stream. Molten metal- 2,738,548 Patented Mar. 20,1956 lic globules are thus allowed to drop directly into the inside ofthe tubular film of liquid from a suitable orifice or dropping box, andthen fall downwardly through the closely confining liquid film to obtainrapid cooling and at least an initial set into substantially sphericalpellets. Preferably, the cross-sectional area or size of the shot insideof the tubular film of cooling fluid is correlated with respect to thesize of the molten globules falling therethrough so that the free oropen area inside of the fluid film is but slightly larger than theultimate diameter of the metallic pellets being formed in thefall'through the elongated film. Thus, there is a fairly rapid coolingof the pellets and it is not necessary to have excessively long or hightubular members and tubular films to pro-v vide the desired cooling andforming of particles.

Also, the present method of forming pellets provides for the formationof steam within the vertical tubular film. The steam is formed as aresult of the close proximity or by the contact of molten globules withthe fluid medium as they fall successively downwardly through thetubular zone, and a resulting upward flow of this steam provides acushioning effect and a slowing down of the fall of molten globules andpellets descending through the confining fluid film. This eifect permitsthe desired cooling within a lesser vertical height than might otherwisebe necessary.

Thus, in a more specific embodiment, the present invention provides amethod for forming substantially spherical metal pellets in a mannerwhich comprises passing molten metal downwardly through an orifice andforming discreet globules of the metal, dropping successive metallicglobules directly from the orifice through a closely confining andconcurrentlyfalling tubularfilm of cooling fluid, effecting the coolingof the globules and the generation of vapor therebelow as they fallthrough the area bounded by the fluid film whereby the generated vaporcushions and slows the fall of said globules as they descend through theconfining fluid film, and discharging resulting cooled substantiallyspheroidal metal pellets from the lower end of the tubular fluid film.

The method of manufacturing and forming desired substantially spheroidalmetallic pellets may be more clearly described and explained byreference to the accompanying drawing and the following descriptionthereof.

Figure 1 of the drawing indicates diagrammatically an apparatusarrangement providing for the dropping of a plurality of molten streamsor globules from a dropping box through a plurality of tubular liquidfilms into a suitable quenching and receiving chamber, from whichresulting spheroidal metal pellets may be withdrawn.

Figure 2 of the drawing shows an enlarged cross-sectional view of thedropping of molten globules through a portion of a forming tube andthrough a descending tubular film of cooling liquid.

Referring now to both Figures 1 and 2 of the drawing, there is shown adropping box 1 suitable for receiving a molten metal by way of inletline 2, which in turn may communicate directly with a suitable meltingfurnacev or the like, not shown. The bottom of the dropping box 1 has aplurality of orifices 3 providing for the formation of molten globules 4which in turn drop successively from each of the orifices directly intothe upper open ends of a plurality of vertically disposed forming tubes5.

In accordance with the present improved invention;

' a ess a fil e up r ends at a h 9? the tabu a members 5 maybe serratedif desired so as to insure a substantially uniform distribution of thefluid circume enti l und e en i i ne wall surface a e ch ubu ar membe 5a d P o i e a renta -wa t q nflo ing film 9. It is also preferable thatthe film 9 be made to flow in a manner providing a substantially thickfilm precluding the possibility of molten globules touching he s d surfae of he ub l mem e 5- t i als within the scope of the improved method ofoperation to utilize a suitable wetting agent in the water or otherfluid medium providing the downwardly flowing tubular lm f liquid 80 t athere is a ubsta ti l unif rm covering of the interior of the tubularmembers 5 and no dry spots therein to which the molten globules may t htse The arrangement as indicated in Figure l of the drawing providesthat the lower ends of each of the tubular members 5 terminate withinthe upper portion of a closed Dt fine-d quenching and receiving chamber10. This chamber 10 has a suitable fluid inlet line 11, having controlvalve 12, and an overflow line 13 which regulates the upper surface of aliquid medium maintained in the chamber 10. Resulting formed pellets andwater or other fluid medium are withdrawn from the lower end of chamber10 by way of line 14 and valve 1 5. The pellets from line 14 may bepassed to suitable screening and pellet recovery apparatus, not shown.The r pper end or top portion of chamber 10 is indicated as being closedand thus provides a steam collecting zone, so that steam which mayresult from the contact of the hot globules with the water in chamber 10may collect and pass upwardly through each of the forming tubes 5 andwithin the confines of the tubular fluid film 9. The water or otherfluid medium which is passed downwardly through the tubular member 5, asthe fluid film 9, discharges from the lower end of each of the tubularmembers 5 as a circumferential film around each of the streams ofdropping pellets and adds to the liquid medium maintained in chamber 10.

Referring now specifically to Figure 2 of the drawing, the moltenglobules 4 are indicated diagrammatically as falling successivelythrough the ring-like or tubular fluid film 9 within tube 5 such thatthey are cooled relatively rapidly by the fluid medium comprising film9. The lower and outer periphery of the globules 4, particularly whilethey are at a high temperature and in a molten state, will effect therapid vaporization of a minor portion of the fluid film and will providesome steam or vapor directly below the leading edge or bottom portion ofthe peripheral surface of each globule. This steam in turn tends toprovide a slowing of the rate of fall or descent of each of theparticles whereby each of the globules and resulting pellets aremaintained within the length of the tubular film 9 and tube member 5 fora longer period of time thanthey would if they were allowed to fallentirely freely with no steam cushioning effect or rising countercurrentflow of steam. The length of the tubular member 5 and the tubular fluidfilm 9 must of course be correlated with the type of molten metal beingformed into pellets, and the melting point or other physicalcharacteristics particularly efiecting the cooling and solidification ofthe pellets so that they will be permitted to be suifijcienly solidifiedprior to leaving the lower end of tube 5 and entering the quenchingliquid in a suitable receiving chamber. 7 i

It is to, be understood that the present drawing is diagrammatic andthat the apparatus shown is not to be considered limiting, and further,that various minor mod- 4 tisatipa may be made in the a pa atus 9! itsarra s?- ment within the scope of the present invention. The tu' bularmembers 5 are preferably round so that the interior fluid film 9 islikewise ring-like or of a cylindrical form, however, in some instancesit may be desirable to provide a tubular member having a corrugatedsurface and in turn provide a descending fluid film therein which has anirregular cross-section, rather than a true ring-like film with acircular inner area. Also, it is to be noted that the present drawingindicates a closed top receiving chamber 10 so that there is a steamcollecting zone providing for the upward flow of such steam that may beformed in chamber 10 through the plurality of forming tubes 5 andcountercurrent flow with respect to the descending molten globules andpellets. However, where sufficient vapor or steam is formed directlywithin the flow path of the pellets and within the confines of thedescending fluid film 9 to provide the desired cushioning and slowingdown of the free fall of the pellets, then it may be unnecessary toprovide a closed top receiving chamber 10. i

I claim as my invention:

l. A method for producing metal pellets which comprises passingsuccessive globules of molten metal down,- wardly through the open spacewithin a closely confining, downwardly moving, vertically elongatedtubular film of cooling liquid, cooling and solidifying the globulesduring their descent through said space and discharging the resultantmetal pellets from the lower confines of said tubular film.

2. The method of claim 1 further characterized in that said liquid isvaporizable at the temperature of the molten metal globules whereby avapor is formed in and rises through the space within the tubular filmto cushion the fall of the globules as they descend through said space.

3. The method of claim 2 further characterized in that said liquidcomprises water.

4. A method for producing substantially spherical aluminum pellets whichcomprises passing successive globules of molten aluminum downwardlythrough the open space within a closely confining, downwardly moving,vertically elongated tubular film of water, cooling and solidifying theglobules during their descent through end of the tubular member, acollecting chamber at the lower end of said member, and means formaintaining a continuous, downwardly moving film of liquid over theinner walls of the tubular member in close proximity to the metalglobules within said member.

References Cited in the file of this patent UNITED STATES PATENTS251,092 Bragg Dec. 20. 1881 496,044 Deniston Apr. 25, 1893 1,393,383Linebarger Oct, 11, 1921 1,837,869 Jewett et a1 t Dec. 22, 1931 0 MorrisAp 2, 19.40 2,209,519 Halbrock et al. July 30, 1 940 2,230,617 Hoar Feb.4, 1941 2,394,727 Taylor Feb. 12, 1946

1. A METHOD FOR PRODUCING METAL PELLETS WHICH COMPRISES PASSINGSUCCESSIVE GLOBULES OF MOLTEN METAL DOWNWARDLY THROUGH THE OPEN SPACEWITHIN A CLOSELY CONFINING DOWNWARDLY MOVING, VERTICALLY ELONGATEDTUBULAR FILM OF COOLING LIQUID, COOLING AND SOLIDIFYING THE GLOBULESDUR-